1. Field of the Invention
The present invention relates to an information display device for displaying information necessary for taking a photograph in a camera viewfinder.
2. Description of the Prior Art
Until now it has been common to display the shutter time, the aperture value, and so on in the viewfinder of a camera. It is essential, particularly for a camera with automatic exposure control, to display a proper exposure value. In addition, conventional cameras also include display alarms which indicate when the amount of light is beyond the available exposure control range, a display for flash photography, and so on, but other data convenient for taking a photograph are rarely displayed.
Besides the above facts, there are many other values which the photographer has to select and confirm before taking a photograph. Among these are the picture angle, the exposure aperture, a shutter time for the safety manual camera holding range and finally, the focal length of the lens.
The picture angle is displayed in the sight field of the viewfinder and can satisfactorily be confirmed in a single lens reflex camera with an efficient viewfinder. As for the selection of the exposure amount, the combination of the shutter time with the aperture value for proper exposure is automatically calculated and displayed in the viewfinder in many modern automatic exposure control cameras. The exposure value is calculated only for the ASA sensitivity of the film in the camera, regardless of the latitude of the film. However, there is no display for judging the exposure factor when one wishes to overexpose or underexpose an object. Also, there is no display showing a safe manual camera holding range of shutter times based on the focal length of the lens mounted when the camera is hand-held.
To determine the focal depth of the lens, it is necessary to use the scale provided on the lens barrel. This is inconvenient to do after the lens has been focused so that an operator rarely bothers to find or confirm this value.
Consequently, although the selection of the picture angle can be made visually by looking through the viewfinder, other functions, such as the selection of the exposure amount, the selection of the shutter time within the safe manual camera holding (i.e., hand held) range and confirmation of the focal depth require other means such as reading the scales on a setting member outside the viewfinder.
A purpose of the present invention is to offer a device by means of which the shutter time range in the safe manual camera holding limit is displayed in accordance with the focal length of the photographic lens, while the shutter time value for controlling the exposure is also displayed, and by comparing both of the above displays, it may easily be determined whether the shutter time is in the safe manual camera holding range.
Another purpose of the present invention is to offer a device which displays the allowable exposure range in accordance with the kind of film, while the exposure value for controlling the exposure is displayed. By comparing these two displays, it may easily be determined whether the exposure value is in the exposure amount allowance range.
Further, another purpose of the present invention is to offer a device which displays the focal depth range in accordance with the aperture value information as well as with the distance information. The distance is displayed in accordance with the distance information, and by comparing the two displays, one can easily judge whether the distance is in the focal depth range.